Over 8 million Americans each year search online for assistance with quitting smoking. Current evidence suggests the use of modern interactive smoking cessation websites results in only a modest increase in short-term abstinence. In addition to serving as a direct channel to provide assistance, the Internet may also serve as a means to connect individuals seeking help in quitting to more established evidence-based behavioral and pharmacological treatments. Smokers who receive a combination of counseling and medications double to triple their likelihood of success, but there has been little prior study of strategies to increase use of evidence-based interventions as part of an online smoking cessation program. We propose a 3-group randomized controlled trial to determine the efficacy and cost-effectiveness of providing access to free nicotine patches, with or without linkage to proactive telephone counseling, as adjuncts to Internet-assisted tobacco treatment. Smokers searching online for help quitting (N=2,475) will be recruited and randomized to receive either (1) online smoking cessation services, (2) online cessation services plus access to free nicotine patches, or (3) online cessation services with access to free patches contingent upon participation in proactive telephone counseling. The primary outcome will be self-reported 6- month prolonged abstinence measured at 9-month evaluation follow-up. Cost-effectiveness analyses will examine the cost per quit, cost per quality year of life saved (QUALY), and employer return on investment (ROI) for the proposed interventions. The exploratory aims of this study are to examine potential mediators and moderators of intervention effects. An examination of potential mediators will identify key psychological and behavioral processes (i.e. medication adherence, self-efficacy, etc.) that underlie how the interventions affect the process of quitting and offer guidance regarding key targets for future research. An examination of potential moderators (i.e. level of dependence, income, gender) is critical because this will identify candidate subgroups for which the proposed interventions may be more effective and cost-effective. This study will answer important questions for state health departments, health plans, large employers, and other entities that are seeking cost-effective strategies for improving the delivery of tobacco treatment services. Findings from this study have the potential to influence future implementation of the U.S. National Action Plan for Tobacco Cessation that currently calls for universal access to pharmacological tobacco treatments as part of phone-based, but not web-based, cessation programs.